1. Field of the Invention
The present invention relates generally to pressure responsive valve assemblies which may be of the pressure relief or shutdown type. More particularly, the present invention concerns pressure responsive valves that are equipped with a rupture disk and a pressure-actuated unit which serves to both actuate the valve and to rupture the disk when the preselected valve set point pressure is exceeded. The valve assembly is particularly suitable for use in a bypass arrangement. The present invention also concerns a rupture disk apparatus for use in the valve assembly.
2. Discussion of Prior Art
Those ordinarily skilled in the art will appreciate that conventional pressure responsive valve assemblies present numerous problems. Particularly, pressure responsive valves tend to be expensive and, in some instances (e.g., inline rupture disks), large and unwieldy. Several conventional pressure responsive valves utilize structure for controlling valve actuation that essentially makes it impractical to use a single valve design for various set pressures. That is to say, a number of conventional valve designs require considerable modification to reconfigure the valve for actuation at different set pressure points. Some conventional valve designs present the risk of spillage and consequent plant contamination, particularly when replacement or reclosure of the valve requires disassembly of the piping to which the valve is connected. There are also concerns that some traditional valve actuating units provide only partial, incomplete valve actuation and that such actuation is probably insufficient to allow rapid and complete venting of the protected conduit or the like. These and other problems are identified in our copending application for U.S. Pat. Ser. No. 09/276,426, filed Mar. 25, 1999, entitled RUPTURE DISK CONTROLLED MECHANICALLY ACTUATED PRESSURE RELIEF VALVE ASSEMBLY, assigned of record to the assignee of the present invention.
Our prior application is directed to a valve assembly design that utilizes a rupture disk to control valve actuation. This arrangement permits the use of a small, easily replaceable rupture disk that can be manufactured to achieve relatively precise, reliable pressure set points for the valves over a wide range of set points and valve sizes. However, our prior application focused on the use of a mechanical actuating unit that contacted and caused the disk to rupture when the valve member experienced an elevation in pressure beyond the predetermined set pressure. In this respect, although the mechanically actuated valve design disclosed in our prior application addresses virtually every one of the problems associated with conventional pressure responsive valves, it has been determined that this design presents a few practical limitations.